1. Field of the Invention
This invention relates, in general, to electrical regulator apparatus and, more specifically, to phase-angle regulators.
2. Description of the Prior Art
Phase-angle regulators are utilized in electrical power distribution systems to correct the phase angle difference between two parallel connected electrical transmission systems and thereby control the power flow between the two systems so that each can be loaded to its maximum capacity. Conventional phase-angle regulators insert a series voltage between the two transmission systems that is in quadrature with the line-to-neutral voltage of one of the systems. The series voltage produces a phase shift whose magnitude varies with the magnitude of the series voltage typically induced through tap changing means on the regulator.
A conventional type of phase-angle regulator, as shown in U.S. Pat. No. 3,690,739 which is assigned to the assignee of the present invention, uses a series transformer having a single series winding per phase. In this type of phase regulating circuit, the load voltage increases in magnitude as the phase angle introduced by the phase-angle regulator increases in magnitude. This has adverse effects since it is desirable to closely match the magnitudes of the load and source voltages when tying the two electrical transmission systems together.
Another common type of phase-angle regulator utilizes a series transformer having a center-tapped series winding. In this type of configuration, the load and source voltages are equal, however, it is difficult to design the center-tapped series winding with sufficient electrical insulation from the ends of the winding to the center tap. It is possible to bring the tap out of the transformer tank through a bushing and limit the voltage across each half winding section by lightning arresters; however, this is expensive and creates additional problems in higher voltage units.
Thus, it would be desirable to provide a phase-angle regulator having a single series winding per phase in which the variation between the magnitudes of the load and source voltages is minimized over the range of phase angles provided by the phase-angle regulator.
It would also be desirable to provide such a phase-angle regulator in which a standard tap changer may be utilized to provide the proper orientation or phase angle of the series voltage with respect to the line voltage despite reversal of the phases of the regulator.